1. Field of the Invention
The present invention relates to compositions and methods of use of gemini surfactants to allow better deposition of polymeric soil release agents with surfactant systems. More particularly, the present invention relates to compositions and methods of use of low concentrations of gemini surfactants to allow the improved deposition of polymeric soil release agents in the presence of typical detergent ingredients, especially highly anionic surfactant systems.
2. Background Discussion
Soil release agents are key ingredients in cleaning, e.g., textile laundry and hard surface such as carpet-cleaning; and textile treating.
These soil release agents are commonly applied during manufacture of clothing or textile fiber. The primary purpose of the soil release agents is to make it easier to clean the textile fibers by home cleaning methods using conventional household machines or cleaners.
For example, in laundering processes normally employed, such as washing in a conventional home washing machine or hand washing with detergent bars, it is usually very difficult to remove soil and/or oily stains from textile material. Moreover, assuming that the undesirable materials are removed from the textile and/or a fairly clean textile material is being washed, soil remaining in the wash water is often redeposited onto the textile material prior to the end of the wash cycle. Hence, when the textile material is removed from the washing machine and subsequently dried, it has not been properly cleaned. Thus, textile material after use rarely assumes a truly clean appearance, but instead tends to gray and/or yellow due to the soil and/or oily materials deposited or redeposited and remaining thereon.
Also, synthetic fibers, and, therefore, fabrics having synthetic fibers incorporated therein or made entirely of synthetic fibers, are hydrophobic and oleophilic. Therefore, the oleophilic characteristics of the fiber permit oil and grime to be readily embedded in the fiber, and the hydrophobic properties of the fiber prevent water from entering the fiber to remove the contaminants from the fiber.
One remedy to the soil removal and soil redeposition problem is to deposit a finish onto the fiber to impart a hydrophilic character to the fiber. Attempts have been made to reduce the oleophilic characteristics of these synthetic fibers by coating the fibers with a coating that is oleophobic, i.e., will hinder the attachment of soil and oil materials to the fibers. Many polymer systems have been proposed which are capable of forming a film around the fibers that constitute the textile material, particularly acid emulsion polymers prepared from organic acids having reactive points of unsaturation. These treating polymers are known as soil-release agents.
Typical of the soil release agents that have been developed for synthetic fibers and fabrics, are the copolymers of ethylene glycol and terephthalic acid for the treatment of Dacron, Fortrel, Kodel and Blue C Polyester, trademarks of various synthetic fibers and fabrics.
Among the leading soil release agents developed for laundering purposes are the polyesters exemplified in U.S. Pat. Nos. 3,962,152; 3,416,952; 4,132,680; 4,201,824; 4,423,557; 4,349,688; 3,959,230; 3,893,929; 3,712,873; and 4,116,885. Generally these agents are polyester polymers containing terephthalate and/or urethane groups to improve water compatibility.
The term "soil-release" in accordance with the present invention refers to the ability of the fabric to be washed or otherwise treated to remove soil and/or oily materials that have come into contact with the fabric. The present invention does not wholly prevent the attachment of soil or oil materials to the fabric, but hinders such attachment and improves the cleanability of the fabric.
Concentrated solutions of soil-release polymers have been padded onto fabrics by textile manufacturers to impart a permanent soil-release finish to the fabric. As the amount of soil-release polymer on the fabric is increased, the ability of the fabric to release soil is increased. However, fabrics with this permanent soil-release finish possess many disadvantages. As the amount of soil-release polymer on the fabric is increased, the fabric has a tendency to become stiff and lose the desirable hand characteristic of the fabric. Thus, the upper limit on the amount of soil-release polymer to be used is determined by economics and the resulting adverse effect on the fabric. Fabrics with a heavy application of soil-release polymer do not have the same desirable appearance and hand as the same fabrics without the soil-release coating. Thus, practically speaking, there is a set concentration range of soil-release agent that can be applied, dictated by commercial requirements.
Some soil-release polymers are effective fabric treating agents even at very low levels on the fabric, at which levels the appearance and hand of the fabric are not adversely affected. Thus, this property offers an ideal method of treating a synthetic fiber containing fabric which would be to reapply a very small amount of soil-release polymer to the fabric each time the fabric is washed.
Moreover, the soil release agent is preferably reapplied when the fabric is washed because the original soil release agent, applied to the fabric during manufacture, washes out after repeated washing by the consumer.
The problem is to get the soil release agent in the detergent solution to adequately deposit and remain on the clothing being washed. A number of theories have been proposed to explain the difficulties encountered when one tries to enhance this soil release agent deposition during wash process. One theory suggests that the urfactants in the detergent may complex with the soil release agent, thus inhibiting he deposition of the agent onto the fabric. Another theory has proposed that the surfactants in the detergent compositions compete with the soil release agents for sites on the fabric. This competition prevents the soil release agents from getting to the fabric.
Anionic surfactants such as alkylbenzenesulfonates, alkylether sulfates, etc., are known to have antagonistic effects on the polymer deposition. These antagonistic effects are further exacerbated because anionic surfactants are generally used at high concentrations for general soil and stain removal performance.
While conventional surfactants generally have one hydrophilic group and one hydrophobic group, recently a group of compounds having at least two hydrophobic groups and at least two hydrophilic groups per molecule have been introduced. These have become known as "gemini surfactants" in the literature, e.g., Chemtech, March 1993, pp 30-33, and J. American Chemical Soc., 115, 10083-10090 (1993) and the references cited therein. Other gemini surfactant compounds, that is, compounds having at least two hydrophilic groups and at least two hydrophobic groups are also disclosed in literature, but often are not referred to expressly as gemini surfactants.
Prior to the present invention, many synergistic benefits of mixtures of gemini surfactants and other ingredients were unknown. It would be a major achievement to provide a detergent composition that would enhance deposition of soil release agents on textile material being washed by the consumer and, thus, provide lasting soil release properties for the life of the material.